This invention relates to a digital image processing system for enhancing the image quality and diagnostic capabilities of conventional medical diagnostic ultrasound imaging systems and, more particularly, to an echocardiography workstation which provides speckle reduction, edge detection, color quantitation, automatic diagnostic features, a built-in Help system for echocardiography, automatic quantitative analysis of left ventricular function, tomographic perfusion display, 3-D analysis, and report generation for improved analysis of echocardiograms.
Diagnostic ultrasound applies high frequency pulsed and continuous sound waves to the body and uses computer-assisted processing of the reflected sound waves to develop images of internal organs and the vascular system. The waves are generated and recorded by transducers or probes that are either passed over or inserted into the body. The resulting images can be viewed immediately on a video display or can be recorded for later evaluation by the physician in continuous or single image formats.
Diagnostic ultrasound imaging is now the preferred imaging modality in radiology, cardiology, and obstetrics and gynecology. Cardiologists and other medical practitioners use cardiac ultrasound imaging, or echocardiography, to evaluate the condition of the heart. Echocardiography is quick, relatively inexpensive, convenient, safe, and non-invasive, and can be performed in real-time in private offices as well as hospitals. The primary drawback of echocardiography has been the difficulty of acquiring good quality images in patients with poor acoustic windows. These patients are estimated to comprise 10-30 percent of the patient population. Moreover, speckle noise and poor resolution can compromise the clinical utility of images of any patient produced by even the most sophisticated ultrasound scanners. With echocardiography, the difficulty of acquiring acceptable images is further compounded by the fact that the region of interest, the heart, has complex motion patterns.
As a result of poor image quality, up to 10 percent of all rest echo studies and up to 30 percent of all stress echo studies of patients are non-diagnostic. The most important factor is the presence of speckle noise, produced by the random pattern of overlapping echos that results from the scattering of the reflected sound waves. This pattern degrades contrast resolution and reduces the ability of an observer to discriminate tissue boundaries and subtle image variations. Techniques for reducing such speckle noise while preserving and enhancing the integrity of the myocardial borders and other cardiac structures remain highly desirable.
Conventional echocardiographic assessment of heart function requires the delineation of the endocardial borders throughout the cardiac cycle. In the images produced by conventional scanners, these borders are often obscured by speckle, masking, blurring, low contrast and interpolation. In addition, discontinuities frequently appear in the echocardiographic image due to poor lateral resolution, which is inherent to ultrasound imaging because portions of the cardiac border are always located parallel to the illuminating sonic beam. Such border definition difficulties are accentuated when performing stress echo studies, making it very difficult to track the endocardial contours. A robust edge detection/contour tracking algorithm is desired that can be used effectively in both rest and stress echocardiography.
In addition, while there are accepted global and regional quantitative measures of cardiac function, there are currently no effective tools that provide automatic quantitation of segmental cardiac function by echocardiography; rather, there are only qualitative assessment or manual quantitative methods which are time-consuming and subject to observer error. Moreover, previous attempts at displaying cardiac wall motion based on boundary detection systems have improperly delineated the endocardial border and blended other signals between the endocardium and other heart structures, such as papillary muscles, chordae, or mitral valve tissue. It remains desirable to provide reproducible automatic quantitation of global indices and regional wall motion and to display the results in a readily understandable format, such as a color-coded format, whereby the effect of therapy and the evolution of disease may be more readily understood.
Also, at present, there are no systems known to the inventors which provide the physician with automatic interpretation assistance for specific echocardiograms and offer the physician various diagnostic possibilities that are consistent with the available data. Conventional echocardiography review and reporting systems are off-line computer systems which are equipped with graphical tools and data entry screens that facilitate on-screen measurement of digitized images and the generation and archiving of reports. Such systems are not configured to capture video images, to perform image enhancement, edge detection, and 3-D image analysis, or to perform stress echo studies. Such systems are also very expensive. A cost-effective off-line and/or on-line analysis and report generation system remains desirable.
Accordingly, it is desired to provide a user-friendly echocardiography workstation that improves image quality, provides automatic edge detection, quantitates endocardial wall movement, corrects for cardiac translation, calculates 3-D left ventricle volume, and assists the physician with the interpretation of echocardiograms. The present invention has been designed to meet these needs in the art.
The present invention addresses the above-mentioned needs in the art by providing an echocardiography workstation that combines video capture and quad screen display for rest and stress echocardiography, speckle reduction, edge detection, and cardiac contour tracking, automatic diagnostic interpretation assistance, a built-in reference source (HELP) to assist the physician and technologist with evaluating echocardiograms, color quantitation, report generation, and automatic wall motion analysis in a single system. The system also includes an optional 3-D feature which utilizes a spatial locating device to obtain tomographic slices along a reference plane which are used for 3-D reconstruction. The workstation of the invention thus complements conventional cardiac ultrasound scanners to enhance the image quality of echocardiograms and to automate functions that have previously been performed manually, thereby saving physician time and reducing costs, while also improving the capabilities of the cardiac scanner.
The workstation of the invention can be used to digitize the video output of cardiac ultrasound scanners. The user can then apply noise reduction algorithms that not only reduce excessive noise but also enhance the definition of cardiac structures. The enhanced images are further processed by boundary detection algorithms to automatically identify the endocardial border and to track its movement through the cardiac cycle. The resulting delineation of the cardiac wall motion allows the physician to more quickly and accurately evaluate heart function. The system corrects for cardiac translation and the extent of cardiac function (motion) is reproducibly automatically quantitated and displayed in a color-coded format which simplifies the physician""s review process. Also, during the physician""s review process, expert system software assists the physician in the interpretation process by listing the various diagnostic possibilities that are consistent with the available data. A Help system assists the physician with the interpretation of the data by providing descriptions of abnormalities with lists of their known causes.
The workstation of the invention may also be used with spatial locators that register the position and orientation of two-dimensional ultrasound images in a three-dimensional spatial coordinate system. This feature enables the system to perform more accurate calculations of cardiac function. The workstation also provides tomographic analysis software to permit the display of myocardial perfusion data for use in conjunction with ultrasound contrast agents. The invention also includes an R-wave synchronization feature to synchronize images of varying frame lengths and heart rates.
Preferably, the physician interacts with the workstation through a graphical user interface or by voice commands to view images, select alternative processing options, consult reference sources, generate reports from pull-down menus, and store, retrieve, and transmit digitized images and reports.